1. Field of the Invention
The present invention relates to a method for manufacturing piezoelectric actuators and to a piezoelectric actuator.
2. Description of the Related Art
Conventionally, in various technical fields, a piezoelectric actuator has been utilized which drive an object by utilizing deformation of a piezoelectric layer (piezoelectric distortion) when an electrical field acts on the piezoelectric layer. Such a piezoelectric actuator has a piezoelectric layer and two electrodes which sandwich the piezoelectric layer. When a voltage is applied to the two electrodes, an electrical field acts on an active portion of the piezoelectric layer sandwiched by the two electrodes, thereby deforming the active portion.
Accordingly, in order to apply a voltage to the two electrodes which sandwich the piezoelectric layer, it is necessary to electrically connect the two electrodes with a drive portion such as a driver IC and the like. Then, in order to electrically connect the two electrodes with the drive portion, it is conceivable, for example, to connect a flexible wiring substrate provided with the driver IC to the upper surface of the piezoelectric actuator. In this case, it is necessary to extract wirings from the two electrodes to the surface of the piezoelectric actuator.
As an example, a piezoelectric actuator is known in which extraction electrodes on the surface of the piezoelectric actuator are connected, via through holes, to the inner electrodes arranged inside the piezoelectric layer and thus not exposed to the surface of the piezoelectric layer. For example, in a certain piezoelectric actuator, two piezoelectric layers are stacked on the upper surface of a vibration plate; and an lower constant-voltage electrode, an upper constant-voltage electrode, and individual electrodes are arranged respectively on the upper surface of the vibration plate, the upper surface of the under piezoelectric layer, and the upper surface of the upper piezoelectric layer. Then, the upper surface of the upper piezoelectric layer is exposed as the surface of the piezoelectric actuator, and in addition to the individual electrodes, a first surface electrode and a second surface electrode are arranged on the upper surface of the upper piezoelectric layer. Although the upper constant-voltage electrode and the lower constant-voltage electrode are not exposed to the surface of the piezoelectric actuator, the upper constant-voltage electrode and the lower constant-voltage electrode are electrically connected with the first surface electrode and the second surface electrode via through holes formed in the piezoelectric layers.